I would like to make a video that essentially shows a long exposure progressing as it is exposed. Essentially it would be initially dark and gradually get lighter. Lights that pass in front of the camera would be shown as gradually leaving a trail.
My options that I know of are either:
1) Instead of doing a single long exposure, do many short exposures sequentially and then create a video where each frame additively overlays another photo. This would be challenging because my intervalometer(sic?) is external and would be difficult to configure so that it triggers another picture as soon as the previous picture finishes exposing. Essentially there would be gaps between the photos.
Edit: Actually just occurred to me that for #1, I could just set the exposure to something like 1/10th second, set to continuous, and tape the button down. The only delay between photos would be time to save them.
2) Write a program that processes the sensor data from the raw format, splitting it up into frames based on what the sensor collected at segments of time. I don't know if the raw format supports this. Doing some brief reading on the format, it isn't really clear to me if this is possible or not. That's really the main reason of this post, is determining whether or not the raw format has exposure over time information that would allow this type of post processing. I.e. such that I can recreate the effect of the sensor capturing more and more light over time. I'd rather not spend alot of time figuring out the format/APIs and prototyping a program if it's not even possible.
So I am looking for an answer that indicates if #2 is possible, any alternative suggested solutions on how to accomplish this, or solutions for accomplishing #1.(I don't expect anyone to go out and write a program for me, but just pinging the community's knowledge of a possible existing solution or workaround) I already have a free/open source program for stitching together simple time lapses. For #1 to work, I would need a variation of this that additively overlays subsequent photos. Something that might support tweening would probably eliminate the anomalies causes by the small gaps between each photo.
Please note when you are suggesting software, whether or not it is expensive or not. Doing this as probably a one or two off hobby and would rather not pay a bunch of money for a commercial video effects package, but it won't hurt for posterity's sake in case others with the same question that come across this post are willing to shell out the big bucks.